Method and apparatus for preventing pulsations

Claim 1

A peristaltic fluid-infusion finger pump apparatus comprising: a peristaltic fluid-infusion finger pump which includes a plurality of fluid-infusion finger members arranged in an array of first to last stage fluid-infusion members each having a respective cam hole, cam means including a rotatable cam shaft and a plurality of eccentric cams mounted on said cam shaft for rotation with said cam shaft and stacked on said cam shaft to form a stacked cam block, said cam shaft being rotatable about a longitudinal rotation axis thereof, said eccentric cams being arranged as first to last stage eccentric cams respectively received in said cam holes of said fluid-infusion finger members, said eccentric cams being shifted from each other on said cam shaft through a predetermined angle; each of said eccentric cams driving a respective fluid-infusion member through a given stroke, each of said eccentric cams having at a maximum stroke section thereof an arc-shaped cam surface portion having a curvature the radius of which is equal to that of a right circle formed with a rotation axis of said cam shaft as a center, and an outer circular contour line formed by the curvature of the stacked cam block being equal to the right circle at an upper end view; a pressure plate facing said array of said first to last stage fluid-infusion finger members with an elastic tube clamped therebetween; driving means coupled to said cam shaft to rotate said cam shaft together with said eccentric cams, whereby said fluid-infusion finger members are successively moved through a given stroke to apply a peristaltic movement to said elastic tube when said eccentric cams are rotated together with said cam shaft to infuse fluid through said elastic tube, said infused fluid having small fluid-infusion pulsations; and pulsation correction means disposed at an outlet side of said peristaltic fluid-infusion finger pump, said pulsation correction means including: at least one pulsation correction finger member having a cam hole therein; and at least one further eccentric cam received in said cam hole of said at least one pulsation correction finger member, said at least one further eccentric cam being mounted on said cam shaft and being rotatably driven by said cam shaft; said at least one pulsation correction finger member being moved by said at least one further eccentric cam and being coupled to said elastic tube for applying a pulsation waveform opposite to the waveform of fluid-infusion pulsations occurring on the outlet side of said peristaltic pump to said elastic tube to substantially cancel out said fluid-infusion pulsations.